1. Field of the Invention
This invention relates to a dental impression tray assembly and a method of preparing a dental impression tray for use.
2. Description of the Related Art
Dental impression trays are often used by dentists, orthodontists, prosthodontists and others engaged in various fields of dentistry for obtaining a model or replica of selected areas of a patient""s oral cavity. For example, a dentist or prosthodontist may desire to have a model of an area of a patient""s oral cavity where one or more teeth are missing or damaged, so that suitable replacement teeth may be made in the lab using the model as a guide. In practice, the replacement teeth may be fitted by trial and error on the model and adjusted in size and shape as needed until a satisfactory size and shape are attained.
As another example, orthodontists often use models of a patient""s teeth to study malformations of the teeth and jaws and plan a course of treatment. In some instances, the orthodontist may use models to trial fit one or more orthodontic appliances that will be used in the oral cavity to move teeth to desired positions. In other instances, models may be used to pre-position a set of orthodontic brackets and associated archwires that are later affixed to the patient""s actual dental arches by a technique known as indirect bonding. Models are also used by orthodontists as well as other dental practitioners to serve as a permanent record of a patient""s teeth before and after treatment, and sometimes at selected intervals during the treatment program.
The use of dental models provides significant advantages for both the dental practitioner and the patient. Models enable the dental practitioner to adjust the shape and size of replacement teeth and tooth restorations and to adjust the position of orthodontic appliances and the like in the practitioner""s laboratory or in an outside laboratory as desired and during a time that is most convenient for the dentist or lab personnel. Moreover, such initial size, shape and position adjustments can be carried out without requiring the patient to wait in the dental chair. Once a satisfactory fitting of the replacement teeth, restoration or orthodontic appliances is obtained on the model, the practitioner can readily install the same in place in the patient""s oral cavity with few or no additional adjustments in many instances.
To obtain a dental model, an impression of desired areas of the patient""s oral cavity is first obtained. To prepare an impression, a quantity of curable dental impression material is placed in an impression tray, and the tray is then positioned in the patient""s oral cavity such that the impression material fills and surrounds the selected area of interest of the oral cavity. Once the impression material has cured, the impression material along with the tray is removed from the oral cavity.
To make a dental model from the impression, a second curable material is poured or otherwise placed in the cured impression material. Once the second material has cured, the impression material is removed from the resulting model. When made properly, the model provides an accurate physical replica of selected areas of the patient""s tooth structure as well as adjacent portions of the patient""s gingiva if desired.
A variety of dental impression trays are available to hold dental impression material as impressions are made. Some dental impression trays have an overall, generally xe2x80x9cUxe2x80x9d-shaped configuration in plan view that matches the overall, generally xe2x80x9cUxe2x80x9d-shaped configuration of the patient""s upper or lower dental arch. Other impression trays have an overall, generally xe2x80x9cJxe2x80x9d-shaped configuration in plan view for making an impression of one quadrant of the patient""s oral cavity (i.e., the right or left half of either the patient""s upper dental arch or lower dental arch). Still other impression trays have a generally straight configuration in plan view and are particularly useful in instances where an impression of areas representing less than a complete quadrant is needed.
Typically, a certain area of the dental impression tray serves as a receptacle for receiving dental impression material. In many dental impression trays, the receptacle comprises a channel having a generally xe2x80x9cUxe2x80x9d-shaped configuration in views transverse to the longitudinal axis of the channel (i.e., in reference planes perpendicular to the occlusal or xe2x80x9cbitexe2x80x9dplane of the patient). Other dental impression trays simply have a flat or generally flat surface for receiving the impression material. Some dental impression trays such as the tray described in U.S. Pat. No. 4,445,854 have upwardly-facing receptacles and downwardly-facing receptacles so that impressions of the upper and lower dental arch can be simultaneously obtained.
Dental impression trays are commercially available in a variety of materials. Some impression trays are made of metal such as stainless steel or aluminum. Other impression trays are made of a rigid plastic material such as polyethylene or polypropylene, or made of polystyrene foam (such as xe2x80x9cSTYROFOAMxe2x80x9d brand polystyrene foam from Dow Chemical Company). Examples of impression trays made of a thermoplastic material that is malleable at elevated temperatures are described in U.S. Pat. Nos. 5,040,976 and 5,026,278.
A variety of dental impression materials are also commercially available. Elastomeric impression materials are generally preferred because the flexibility of the elastomeric material when cured enables the material to be readily removed from the oral cavity even when undercut areas, recesses and the like are present in the tooth structure. However, non-elastomeric impression material (such as plaster of Paris) has also been used in the past to a limited extent.
Elastomeric dental impression materials are often considered to fall in one of five major classes: reversible hydrocolloids, irreversible hydrocolloids, polysulfides, silicones and polyethers, of which the last four are thermosetting. An example of an irreversible hydrocolloid impression material is xe2x80x9cUNIJEL-IIxe2x80x9d brand alginate impression material from 3M Unitek Corporation. An example of a silicone dental impression material is xe2x80x9cEXPRESSxe2x80x9d brand impression material from 3M Company.
Often, a means is provided to securely connect the impression material to the impression tray so that the impression material does not inadvertently detach from the receptacle of the impression tray. For example, when removing an impression tray bearing a quantity of elastomeric impression material from the patient""s oral cavity, a significant force must sometimes be exerted on the tray in order to cause the cured impression material to flexibly deform as needed to disconnect from undercut areas or recesses of certain tooth structure. In such instances, the impression material should remain securely connected to the impression tray so that both the material and the tray are removed as a single unit from the oral cavity.
Some impression trays have holes or perforations placed along the receptacle to provide a mechanical means for coupling the impression material to the tray. In other instances, an adhesive is used to chemically bind the impression material to the receptacle of the tray. An example of a tray adhesive used in connection with alginate impression material is xe2x80x9cHOLDxe2x80x9d brand tray adhesive from Teledyne Getz. Tray adhesives are particularly useful for alginate and other hydrocolloid impression material that have little, if any, adhesive qualities.
Tray adhesives are conventionally used by the dental practitioner by applying the adhesive to the receptacle of the tray that receives the impression material immediately before the impression is to be taken. The impression material is then placed in the receptacle and the impression is made in the manner described above.
U.S. Pat. No. 5,772,432 describes an improved dental impression tray with a receptacle for receiving the dental impression material. The receptacle is coated with an adhesive to enhance the bond between the impression material and the tray. The adhesive is applied to the tray body at least 16 hours before the impression material is placed in the receptacle. Advance coating of the adhesive onto the tray body provides a higher bond strength between the impression material and the tray than would otherwise be observed. Additionally, precoating of the impression tray by the manufacturer reduces the risk that the patient will experience a burning sensation or irritation due to one or more solvents that might otherwise volatilize from the tray adhesive during use in the oral cavity, or that might be caused by direct contact of the tray adhesive with the patient""s gingiva.
However, some impression materials are somewhat fluid and may leak through holes in the tray, causing a nuisance to the practitioner and possibly also to the patient. The problem of leakage is particularly noticeable when alginate impression materials are mixed by the practitioner to a somewhat thin, runny consistency. Unfortunately, the use of a tray adhesive does not significantly reduce the likelihood of dripping of impression materials through the holes, especially in instances when the impression material is relatively thin and fluid.
As can be appreciated, there is a need in the art for an impression tray that provides enhanced retention of impression material in the tray receptacle and yet avoids the problem of leakage of impression material from the receptacle, even when relatively fluid impression materials are used. Preferably, such an impression tray would be relatively inexpensive and yet adaptable to a variety of different uses according to the preferences of the practitioner for the situation at hand.
The present invention is directed toward a dental impression tray assembly that has a removable liner. The liner is adapted to extend across at least some of the holes in the tray in order to substantially prevent leakage of impression material through the holes. Preferably, the liner is removably connected to the impression tray so that the practitioner can use the tray without the liner if desired.
In more detail, the present invention is one aspect is directed toward a dental impression tray assembly. The assembly includes a dental impression tray having wall portions defining a receptacle for receiving a quantity of dental impression material. At least some of the wall portions include a number of holes. The assembly also includes a liner that is removably connected to the impression tray. The liner extends across at least some of the holes.
In another aspect, the present invention is directed toward a dental kit. The kit includes a dental impression tray having wall portions defining a receptacle for receiving a quantity of dental impression material. At least some of the wall portions include a number of holes. The kit also includes an impression tray liner for connection to the impression tray. The liner extends across at least some of the holes when connected to the impression tray.
The present invention is also directed to a dental impression tray liner. The liner comprises a barrier sheet and an adhesive extending over at least part of the barrier sheet. The barrier sheet includes a portion having a generally xe2x80x9cUxe2x80x9d-shaped configuration for connection to the dental impression tray.
Another aspect of the present invention is directed toward a method of preparing a dental impression tray for use. The method includes the act of selecting an impression tray suitable for taking an impression of oral structure of interest. The method also includes the act of connecting a liner to the tray in order to cover at least one hole in the tray.
These and other aspects of the invention are described in more detail in the text that follows and are illustrated in the accompanying drawings.